U.S. patent number 6,549,785 [Application Number 09/372,086] was granted by the patent office on 2003-04-15 for method for improving performances of a mobile radiocommunication system using a power control algorithm.
This patent grant is currently assigned to Alcatel. Invention is credited to Pascal Agin.
United States Patent |
6,549,785 |
Agin |
April 15, 2003 |
Method for improving performances of a mobile radiocommunication
system using a power control algorithm
Abstract
A method for improving performances of a mobile
radiocommunication system using a power control algorithm for
controlling a transmit power according to a transmission quality
target value, and an adjustment algorithm for adjusting the
transmission quality target value according to transmission
requirements, the method including, upon the occurrence of a change
in the transmission requirements, bypassing the adjustment
algorithm, by applying a corresponding change to the transmission
quality target value, so as to adjust it in an anticipated way.
Inventors: |
Agin; Pascal (Sucy en Brie,
FR) |
Assignee: |
Alcatel (Paris,
FR)
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Family
ID: |
8242057 |
Appl.
No.: |
09/372,086 |
Filed: |
August 11, 1999 |
Foreign Application Priority Data
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Jul 13, 1999 [EP] |
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99401766 |
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Current U.S.
Class: |
455/522;
455/67.11; 370/318; 455/69; 455/70; 370/335; 370/320 |
Current CPC
Class: |
H04W
52/241 (20130101); H04W 52/12 (20130101); H04W
52/20 (20130101); H04W 52/54 (20130101); H04W
52/50 (20130101); H04W 52/228 (20130101); H04W
52/26 (20130101); H04W 52/44 (20130101); H04W
52/225 (20130101); H04W 52/288 (20130101) |
Current International
Class: |
H04B
7/005 (20060101); H04Q 007/20 (); H04B
007/00 () |
Field of
Search: |
;455/69,70,13.4,127,522,296,298,343,422,423-425,9,10,504,505,67.1,67.6,68,226.1
;370/317,318,332,335,342,320 ;375/148,224-227,252,296,297,219 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 853 393 |
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Jul 1998 |
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EP |
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WO 98/58461 |
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Dec 1998 |
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WO |
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00/45528 |
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Aug 2000 |
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WO |
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Other References
A Sampath et al, "On Setting Reverse Link Target SIR in a CDMA
System" IEEE Vehicular Technology Conference, US, New York, IEEE,
vol. CONF. 47, pp. 929-933 XP000736744. .
EPO Communication dated Aug. 26, 2002 including European Search
Report completed Aug. 20, 2002..
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Primary Examiner: Legree; Tracy
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
What is claimed is:
1. A method for improving performances of a mobile
radiocommunication system using a power control algorithm for
controlling a transmit power according to a transmission quality
target value, and an adjustment algorithm for adjusting said
transmission quality target value according to transmission
requirements, said method including, upon the occurrence of a
change in said transmission requirements, applying a corresponding
change to said transmission quality target value, so as to adjust
it in an anticipated way, said adjustment in an anticipated way
corresponding to adjustment based on a fixed criteria in addition
to said adjustment algorithm.
2. A method according to claim 1, further including, upon the
occurrence of a change in said transmission requirements, applying
a corresponding change to said transmit power, so as to control it
in an anticipated way, said control in an anticipated way
corresponding to control based on a fixed criteria in addition to
said power control algorithm.
3. A method according to claim 1, wherein said change in
transmission requirements includes a change from a non-compressed
mode to a compressed mode, and wherein said corresponding change
includes an increase in said transmission quality target value, to
be applied before a compressed frame.
4. A method according to claim 1, wherein said change in
transmission requirements includes a change from a non-compressed
mode to a compressed mode, and wherein said corresponding change
includes an increase in said transmission quality target value, to
be applied after a transmission gap of a compressed frame.
5. A method according to claim 1, wherein said change in
transmission requirements includes a change from a compressed mode
to a non-compressed mode, and wherein said corresponding change
includes a decrease in said transmission quality target value, to
be applied after a compressed frame.
6. A method according to claim 1, wherein said change in
transmission requirements includes a change from a compressed mode
to a non-compressed made, and wherein said corresponding change
includes an increase in said transmission quality target value, to
be applied during one or more recovery frames following a
compressed frame.
7. A method according to claim 1, wherein said transmission quality
is represented by a signal-to-interference ratio.
8. A method according to claim 1, wherein said mobile
radiocommunication system is of CDMA type.
9. A method according to claim 1, wherein said power control is
performed in the uplink transmission direction of said mobile
radiocommunication system.
10. A mobile radiocommunication network entity comprising, for
performing a method according to claim 1 in the uplink transmission
direction of said mobile radiocommunication system: means for, upon
the occurrence of a change in said transmission requirements,
applying a corresponding change to said transmission quality target
value, so as to adjust it in an anticipated way, said adjustment in
an anticipated way corresponding to adjustment based on a fixed
criteria in addition to said adjustment algorithm.
11. A method according to claim 1, wherein said power control is
performed in the downlink transmission direction of said mobile
radiocommunication system.
12. A mobile radiocommunication network entity for performing a
method according to claim 11 in said down link transmission
direction, further including: means for, upon the occurrence of a
change in said transmission requirements, applying a corresponding
change to said transmit power, so as to control it in an
anticipated way, said control in an anticipated way corresponding
to control based on a fixed criteria in addition to said power
control algorithm.
13. A mobile station comprising, for performing a method according
to claim 1 in the downlink transmission direction of said mobile
radiocommunication system: means for, upon the occurrence of a
change in said transmission requirements, applying a corresponding
change to said transmission quality target value, so as to adjust
it in an anticipated way, said adjustment in an anticipated way
corresponding to adjustment based on a fixed criteria in addition
to said adjustment algorithm.
14. A mobile station for performing a method according to claim 9,
in said uplink transmission direction, further comprising: means
for, upon the occurrence of a change in said transmission
requirements, applying a corresponding change to said transmit
power, so as to control it in an anticipated way, said control in
an anticipated way corresponding to control based on a fixed
criteria in addition to said power control algorithm.
15. A mobile radiocommunication network entity comprising, for
performing a method according to claim 11 in said downlink
transmission direction: means for signalling said corresponding
change to a mobile station.
16. A mobile radiocommunication network entity according to claim
15, wherein, said change in the transmission requirements including
a change from a non-compressed mode to a compressed mode, and/or
from a compressed mode to a non-compressed mode, said means include
means for signalling a component of said corresponding change which
corresponds to that part of said change in transmission
requirements which is not due to the bitrate increase during
compressed frames.
17. A mobile radiocommunication system including a mobile
radiocommunication network entity according to any one of claims 15
or 19.
18. A mobile radiocommunication network entity comprising, for
performing a method according to claim 11 in said downlink
transmission direction: means for signalling to a mobile station
the occurrence of a change in said transmission requirements.
19. A mobile radiocommunication network entity comprising, for
performing a method according to claim 11 in said downlink
transmission direction: means for signalling said corresponding
change to a mobile station, together with the signalling of the
occurrence of a change in the transmission requirements.
20. A mobile radiocommunication network entity according to claim
19, wherein, said change in the transmission requirements including
a change from a non-compressed mode to a compressed mode, and/or
from a compressed mode to a non-compressed mode, said means include
means for signalling said corresponding change together with the
signalling of compressed mode parameters.
21. A mobile radiocommunication network entity according to claim
20, wherein said means include means for performing said signalling
for each compressed frame.
22. A mobile radiocommunication network entity according to claim
20, wherein, in the case where compressed frames occur
periodically, said means comprise means for performing said
signalling once for all, for all compressed frames of a thus
defined period.
23. A mobile radiocommunication system including at last a
transmitting entity and a receiving entity for performing a method
according to claim 1, and wherein means are provided in one of said
entities, for, upon the occurrence of a change in said transmission
requirements, applying a corresponding change to said transmission
quality target value, so as to adjust it in an anticipated way,
said adjustment in an anticipated way corresponding to adjustment
based on a fixed criteria in addition to said adjustment
algorithm.
24. A mobile radiocommunication system according to claim 23,
wherein means are further provided in one of said entities, for,
upon the occurrence of a change in said transmission requirements,
applying a corresponding change to said transmit power, so as to
control it in an anticipated way, said control in an anticipated
way corresponding to control based on a fixed criteria in addition
to said power control algorithm.
25. A mobile radiocommunication system according to claim 23,
wherein means are provided in a first one of said entities for
determining and/or updating said corresponding change.
26. A mobile radiocommunication system according to claim 25,
wherein means are provided in a second one of said entities for
signalling to said first entity previous values necessary for
determining and/or updating said corresponding change.
27. A mobile radiocommunication system according to claim 23,
wherein means are provided in a second one of said entities for
signalling to a first one of said entities said corresponding
change.
28. A mobile radiocommunication system according to claim 23,
wherein means are provided in a second one of said entities for
signalling to a first one of said entities the occurrence of a
change in said transmission requirements.
29. A mobile radiocommunication system according to claim 23,
wherein means are provided in a second one of said entities for
signalling said corresponding change to a first one of said
entities together with the signalling of the occurrence of a change
in the transmission requirements.
30. A mobile radiocommunication system according to claim 23,
wherein means are provided in any one of said two entities for
recording said corresponding change.
31. A mobile radiocommunication system according to claim 23,
wherein one of said two entities is a mobile radiocommunication
network entity.
32. A mobile radiocommunication system according to claim 23,
wherein one of said two entities is a mobile station.
33. A method for improving performances of a mobile
radiocommunication system using a power control algorithm for
controlling a transmit power according to a target SIR, and an
adjustment algorithm for adjusting said target SIR according to
transmission requirements, wherein, in compressed mode, the target
SIR is increased in compressed frames and/or in frames immediately
following the compressed frames.
34. A method for improving performances of a mobile
radiocommunication system using a power control algorithm for
controlling a transmit power according to a target SIR, and an
adjustment algorithm for adjusting said target SIR according to
transmission requirements, wherein, in compressed mode, the target
SIR is increased in compressed frames by a target SIR increase due
to the bit-rate increase in compressed frames and by a target SIR
increase due to degraded performances in compressed frames.
35. A method for improving performances of a mobile
radiocommunication system using a power control algorithm for
controlling a transmit power according to a target SIR and an
adjustment algorithm for adjusting said target SIR according to
transmission requirements, wherein, in compressed mode, the target
SIR is increased in frames immediately following the compressed
frames by a target SIR increase due to degraded performances in
frames immediately following the compressed frames.
36. A method for improving performances of a mobile
radiocommunication system using a power control algorithm for
controlling a transmit power according to a target SIR, and an
adjustment algorithm for adjusting said target SIR according to
transmission requirements, wherein a mobile radiocommunication
network entity signals to mobile stations the target SIR increase
which is due to degraded performances in compressed frames and/or
in frames immediately following the compressed frames, by which
mobile stations have to increase the target SIR respectively in
compressed frames and in frames immediately following the
compressed frames.
37. A method according to claim 36, wherein said target SIR
increase is signaled together with other compressed mode
parameters.
38. A mobile station for a mobile radiocommunication system
comprising means for performing a power control algorithm for
controlling a transmit power according to a target SIR, and an
adjustment algorithm for adjusting said target SIR according to
transmission requirements, said mobile station including means for,
in compressed mode, increasing the target SIR in compressed frames
and/or in frames immediately following the compressed frames.
39. A mobile station for a mobile radiocommunication system
comprising means for performing a power control algorithm for
controlling a transmit power according to a target SIR, and an
adjustment algorithm for adjusting said target SIR according to
transmission requirements, said mobile station including means for,
in compressed mode, increasing the target SIR in compressed frames
by a target SIR increase due to the bit-rate increase in compressed
frames, and by a target SIR increase due to degraded performances
in compressed frames.
40. A mobile station for a mobile radiocommunication system
comprising means for performing a power control algorithm for
controlling a transmit power according to a target SIR, and an
adjustment algorithm for adjusting said target SIR according to
transmission requirements, said mobile station including means for,
in compressed mode, increasing the target SIR in frames just
following compressed frames by a target SIR increase due to
degraded performances in frames just following compressed
frames.
41. A mobile station according to any one of claims 38 to 40, said
mobile station further including means for simultaneously
increasing its transmit power by the same amount before the
compressed frames, and decrease it just after the compressed
frames.
42. A mobile radiocommunication system including at least one
mobile station according to any one of claims 38 to 40.
43. A mobile radiocommunication network entity for a mobile
radiocommunication system comprising means for performing a power
control algorithm for controlling a transmit power according to a
target SIR and an adjustment algorithm for adjusting said target
SIR according to transmission requirements, said mobile
radiocommunication network entity including means for signaling to
mobile stations the target SIR increase which is due to degraded
performances in compressed frames and/or in frames immediately
following the compressed frames, by which mobile stations have to
increase the target SIR respectively in compressed frames and/or in
frames immediately following the compressed frames.
44. A mobile radiocommunication network entity according to claim
43, including means for signaling said target SIR increase together
with other compressed mode parameters.
45. A mobile radiocommunication system including at least one
mobile radiocommunication network entity according to any one of
claims 43 or 44.
Description
BACKGROUND OF THE INVENTION
The present invention is generally concerned with mobile
radiocommunication systems.
The present invention is more particularly concerned with power
control techniques used in such systems to improve performances (in
terms of quality of service, of capacity, . . . etc.).
The present invention is in particular applicable to mobile
radiocommunication systems of CDMA ("Code Division Multiple
Access") type. In particular, the present invention is applicable
to UMTS ("Universal Mobile Telecommunication System").
As is known, CDMA systems use two types of power control
techniques, a so-called open-loop power control technique, and a
so-called closed loop power control technique (also called
hereinafter CLPC). These power control techniques may be recalled
for example for the uplink transmission direction, i.e. from MS
("Mobile Station") to BTS ("Base Transceiver Station"). In the
open-loop power control, a MS transmit power is controlled based on
the power received by this MS from a BTS. In the CLPC, a MS
transmit power is controlled based on the transmission quality of
the link between this MS and a BTS, as estimated at this BTS.
The transmission quality of a link between a MS and a BTS depends
on the ratio of the received signal power and the interference
power, also called SIR (Signal-to-Interference Ratio). When the SIR
of a MS is low, or equivalently when the powers of the other MSs
are much higher than its power, its performances dramatically
decrease. The CLPC algorithm enables to keep the SIR of each user
as close as possible to a target SIR.
The principle of the CLPC algorithm is that the BTS periodically
estimates the SIR of the received signal from each MS, and compares
this estimated SIR to a target SIR (SIR.sub.target). If the
estimated SIR is lower than the target SIR, the BTS sends a power
control command to the MS, for the MS to increase its transmit
power. Otherwise, the BTS sends a power control command to the MS,
for the MS to decrease its transmit power.
The target SIR is an important parameter in such systems. Indeed,
if the target SIR value is set to a value higher than necessary,
there is a needless contribution to interference level in the
system, and therefore a needless degradation of the performances of
the system; on the other hand if the target SIR value is set to a
value lower than necessary, the performances of the on-going
communication are degraded.
The target SIR is generally chosen as a function of the required
quality of service, and is currently adjusted by a so-called outer
loop algorithm (as opposed to the preceding one also called inner
loop algorithm). The principle of the outer loop algorithm is to
regularly estimate the quality of service (generally represented by
a bit error rate BER or a frame error rate FER for voice services,
or a block error rate BLER for data packet services) and to compare
the estimated quality with a required quality of service. If the
estimated quality is below the required quality of service, the
target SIR is increased. Otherwise, the target SIR is
decreased.
As opposed to the inner loop algorithm which needs to be rapid to
track the SIR variations as closely as possible, the outer loop
algorithm needs to be slow, since the quality needs to be averaged
over a certain period in order to have a reliable estimate.
Typically, in third generation systems like for example UMTS
("Universal Mobile Telecommunications System"), the SIR of the
received signal is determined and compared to the target SIR every
slot in a frame, while the quality is averaged over several frames
(a slot being an elementary time unit in a data unit, or frame,
transmitted in such a system, the frame duration being typically
equal to 10 ms, and the slot duration to 1/15 of the frame
duration).
Such a slow process may however raise serious problems, in
particular when a so-called compressed mode is used.
The downlink compressed mode has been introduced in UMTS in order
to make possible for a user equipment (UE) to perform measurements
on a frequency different from its downlink transmission frequency.
It consists basically in stopping the downlink transmission during
a certain amount of time (or transmission gap). Simultaneous uplink
and downlink compressed modes can also be used when the measurement
frequency is close to the uplink transmission frequency.
Because the instantaneous bit rate will have to be increased during
compressed frames (by increasing the coding rate or decreasing the
spreading factor), the target SIR also needs to be approximately
increased by the same proportion.
Additionally, since the closed-loop power control is no longer
active during transmission gaps for downlink and uplink, the
performance are significantly degraded, mainly during compressed
frames and recovery frames (frames just following compressed
frames). The degradation can reach several decibels. In order to
keep the same quality of service as in normal (or non-compressed)
mode, this effect would also need to be compensated by increasing
the target SIR during these frames.
However, the outer-loop power control algorithm is a slow process
and several frames will be probably required before changing the
target SIR accordingly. Therefore, it is likely that this process
is too slow to be able to increase the target SIR in compressed and
recovery frames as required. Moreover, the target SIR even risks to
be increased just after compressed and recovery frames where it
would not be needed.
Thus, there is a need for a faster process than the classical
outer-loop algorithm, in compressed mode, to avoid degrading the
performances.
More generally there is a need for a faster process than the
classical outer-loop algorithm, in any case of change in the
transmission requirements, including: change from a non-compressed
mode to a compressed mode, or vice versa, change in required
service (in particular change in the transmission rate), change in
transmission rate, for a given required service (such as for
example data packet services), change in environment conditions
(such as mobile speed, radio propagation conditions, . . . ), . . .
etc.
Thus there is a general need for a more efficient power control, so
as to improve performances.
SUMMARY OF THE INVENTION
An object of the present invention is therefore a method for
improving performances of a mobile radiocommunication system using
a power control algorithm for controlling a transmit power
according to a transmission quality target value, and an adjustment
algorithm for adjusting said transmission quality target value
according to transmission requirements, said method including, upon
the occurrence of a change in said transmission requirements,
bypassing said adjustment algorithm by applying a corresponding
change to said transmission quality target value, so as to adjust
it in an anticipated way.
According to another object of this invention, said method further
includes, upon the occurrence of a change in said transmission
requirements, bypassing said power control algorithm, by applying a
corresponding change to said transmit power, so as to control it in
an anticipated way.
In this way, performances are still improved by enabling the
transmit power to be as quickly as possible close to the new
transmission quality target value.
According to another object of this invention, said change in the
transmission requirements includes a change from a non-compressed
mode to a compressed mode, and said corresponding change includes
an increase in said transmission quality target value, to be
applied before a compressed frame.
According to another object of this invention, said change in the
transmission requirements includes a change from a non-compressed
mode to a compressed mode, and said corresponding change includes
an increase in said transmission quality target value, to be
applied after a transmission gap of a compressed frame.
According to another object of this invention, said change in the
transmission requirements includes a change from a compressed mode
to a non-compressed mode, and said corresponding change includes a
decrease in said transmission quality target value, to be applied
after a compressed frame.
According to another object of this invention, said change in the
transmission requirements includes a change from a compressed mode
to a non-compressed mode, and said corresponding change includes an
increase in said transmission quality target value, to be applied
during one or more recovery frames following a compressed frame
ending with a transmission gap.
According to another object of the present invention, said
transmission quality is represented by a signal-to-interference
ratio.
According to another object of this invention, said mobile
radiocommunication system is of CDMA type.
According to another object of this invention, said power control
is performed in the uplink transmission direction of said mobile
radiocommunication system.
According to another object of this invention, said power control
is performed in the downlink transmission direction of said mobile
radiocommunication system.
Another object of the present invention is a mobile
radiocommunication system including at least a transmitting entity
and a receiving entity for performing such a method, and wherein
means are provided in a first one of said entities, for, upon the
occurrence of a change in said transmission requirements, bypassing
said adjustment algorithm by applying a corresponding change to
said transmission-quality target value, so as to adjust it in an
anticipated way.
According to another object of this invention, means are provided
in said first entity for determining and /or updating said
corresponding change.
According to another object of this invention, means are provided
in a second one of said entities for signalling to said first
entity previous values necessary for determining and/or updating
said corresponding change.
According to another object of this invention, means are provided
in a second one of said entities for signalling to said first
entity said corresponding change.
According to another object of this invention, means are provided
in a second one of said entities for signalling to said first
entity the occurrence of a change in said transmission
requirements.
According to another object of this invention, means are provided
in a second one of said entities for signalling said corresponding
change to said first entity together with the signalling of the
occurrence of a change in the transmission requirements.
According to another object of this invention, means are provided
in any one of said two entities for recording said corresponding
change.
According to another object of this invention, one of said two
entities is a mobile radiocommunication network entity.
According to another object of this invention, one of said two
entities is a mobile station.
Another object of the present invention is a mobile
radiocommunication network entity comprising, for performing such a
method in said uplink transmission direction: means for, upon the
occurrence of a change in said transmission requirements, bypassing
said adjustment algorithm by applying a corresponding change to
said transmission quality targetvalue, so as to adjust it in an
anticipated way.
According to another object of this invention, said mobile
radiocommunication network entity further includes: means for, upon
the occurrence of a change in said transmission requirements,
bypassing said power control algorithm, by applying a corresponding
change to said transmit power, so as to control it in an
anticipated way.
Another object of the present invention is a mobile station
comprising, for performing such a method in said downlink
transmission direction: means for, upon the occurrence of a change
in said transmission requirements, bypassing said adjustment
algorithm by applying a corresponding change to said transmission
quality targetvalue, so as to adjust it in an anticipated way.
According to another object of the present invention, said mobile
station comprises, for performing such a method in said downlink
transmission direction: means for, upon the occurrence of a change
in said transmission requirements, bypassing said power control
algorithm by applying a corresponding change to said transmit
power, so as to control it in an anticipated way.
Another object of this invention is a mobile radiocommunication
network entity comprising, for performing such a method in said
downlink transmission direction: means for signalling said
corresponding change to a mobile station.
According to another object of this invention a mobile
radiocommunication network entity comprises, for performing such a
method in said downlink transmission direction: means for
signalling to a mobile station the occurrence of a change in said
transmission requirements.
According to another object of this invention, a mobile
radiocommunication network entity comprises, for performing such a
method in said downlink transmission direction: means for
signalling said corresponding change to a mobile station, together
with the signalling of the occurrence of a change in the
transmission requirements.
According to another object of this invention, said change in the
transmission requirements includes a change from a non-compressed
mode to a compressed mode, and/or from a compressed mode to a
non-compressed mode, and said signalling is performed together with
the signalling of compressed mode parameters.
According to another object of this invention, said change in the
transmission requirements includes a change from a non-compressed
mode to a compressed mode, and/or from a compressed mode to a
non-compressed mode, and said signaled corresponding change
includes a component which corresponds to that part of said change
in transmission requirements which is due to the transmission gaps
of the compressed frames.
According to another object of this invention, said signalling is
performed for each compressed frame.
According to another object of this invention, in the case where
compressed frames occur periodically, said signalling is performed
once for all, for all compressed frames of a thus defined
period.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects of the present invention will become more
apparent from the following description taken in conjunction with
the accompanying drawings:
FIG. 1 is a diagram intended to illustrate the different steps of a
current power control process (whether in uplink or in
downlink),
FIG. 2 is a diagram intended to illustrate the different steps of a
power control process modified so as to include a method according
to the present invention (whether in uplink or in downlink),
FIG. 3 is a diagram intended to illustrate an example of means
which may be used in a mobile station and in a mobile
radiocommunication network entity to perform a method according to
the present invention, for uplink power control,
FIG. 4 is a diagram intended to illustrate an example of means
which may be used in a mobile radiocommunication network entity and
in a mobile station, to perform a method according to the present
invention, for downlink power control.
MORE DETAILED DESCRIPTION OF THE INVENTION
As recalled in FIG. 1, a current power control process includes an
inner loop algorithm (herein also called power control algorithm) 1
and an outer loop algorithm (herein also called adjustment
algorithm) 2.
The inner loop algorithm 1 includes the following steps: At step
10, a receiving entity estimates the averaged received SIR during a
period T, At step 11, the receiving entity compares this SIR to a
target SIR, SIR.sub.traget, If S/R.sub.22 SR.sub.target, at step 12
the receiving entity sends a "down" power control command to a
transmitting entity, for the transmitting entity to decrease its
power by .delta. dB, where .delta. is the power control step size
of the algorithm, if SIR<SIR.sub.target, at step 13 the
receiving entity sends an "up" power control command to the
transmitter, for the transmitting entity to increase its power by
.delta. dB.
This is periodically repeated, as illustrated by loop 14.
The outer loop algorithm 2 comprises the following steps: at step
15, the receiving entity estimates the averaged received quality
(for example BER) during a period T'.gtoreq.T at step 16, the
receiving entity compares this estimated BER to a target BER
(representing a required quality of service), If
BER>BER.sub.target, at step 17 SIR.sub.target is decreased, if
BER<BER.sub.target, at step 18 SIR.sub.target is increased.
This is periodically repeated, as illustrated by loop 19.
An example of modification of power control process so as to
include a method according to the present invention will be
disclosed in the following. It should however be noted that this
example is not limitative and that the invention might as well be
applied to other examples of algorithms.
In the example of FIG. 2 (where the same references than in FIG. 1
refer to the same elements) a new step 20 is introduced. In this
step 20 there is determined if a change has occurred in the
transmission requirements.
If such a change has not occurred, the outer loop algorithm 2 is
performed as in FIG. 1.
If such a change has occurred, a new step 21 is performed,
according to which a corresponding change is applied to said
SIR.sub.target value, so as to adjust it in an anticipated way, and
thereby improve performances.
Besides, in the example of FIG. 2, if such a change has not
occurred, the inner loop algorithm is performed as in FIG. 1. If
such a change has occurred, a new step 22 is performed, according
to which a corresponding change is applied to the transmit power,
so as to control it in an anticipated way, and therby still improve
performances.
Such corresponding changes, corresponding to such changes in the
transmission requirements, may have predetermined values, which may
be determined in any way.
For example they may be seen as system parameters and be determined
accordingly by the operator of the system. They may also be
prealably determined, in particular by simulation. In either case,
they may be updated during operation. They may also be determined
during operation based on previously obtained values, for example
by averaging. In any case the obtention mode of said predetermined
values should take into account all factors that are likely to
influence said corresponding changes, or combinations of such
factors.
Besides, they may be known in any one of the two entities
(transmitting entity and receiving entity) involved in a power
control process, to be used locally in this entity, or signalled to
the other one of said entities, to be used in this entity.
Besides, they may be determined and/or updated in any of said two
entities, based on statistics on previously obtained values,
available either locally in this entity, or signalled to this
entity by the other one of said entities.
Besides, they may be recorded in any one of said entities, to be
recovered when necessary.
Besides, the occurrence of a change in the transmission
requirements may either be known locally by the entity in charge of
applying the corresponding change or signalled to this latter
entity by the other one of said entities.
Thus, every possibility may be envisaged; therefore the examples
given in this description should be understood as illustrative
only, and having no limitative character.
FIG. 3 is a diagram intended to illustrate an example of means
which may be used in a mobile radiocommunication network entity,
noted 40, and in a mobile station noted 41, to perform a method
according to the present invention, for uplink power control.
A mobile radiocommunication network entity 40, such as in
particular BTS for "Base Transceiver Station" (or Node B in UMTS)
and/or BSC for "Base Station Controller" (or RNC for "Radio Network
Controller" in UMTS), may comprise, for performing said method in
said uplink transmission direction (and further to other classical
means not mentioned here): means 42 for, upon the occurrence of a
change in said transmission requirements, bypassing said adjustment
algorithm, by applying a corresponding change to said transmission
quality target value, so as to adjust it in an anticipated way.
Mobile radiocommunication network entity 40 may also comprise, for
performing said method in said uplink transmission direction (and
further to other classical means not mentioned here): means, also
noted 42 for, upon the occurrence of a change in said transmission
requirements, bypassing said power control algorithm, by applying a
corresponding change to said transmit power, so as to control it in
an anticipated way.
Such corresponding changes, corresponding to such changes in the
transmission requirements, may for example have predetermined
values, which may for example be determined according to any of the
above mentioned possibilities.
In any case, mobile radiocommunication network entity 40 for
example may comprise: means 42' for recording said corresponding
changes.
A mobile station 41 (or User Equipment UE in UMTS) may comprise,
for performing said method in said uplink transmission direction
(and further to other classical means not mentioned here): means 43
for signalling to a mobile radiocommunication network entity the
occurrence of a change in the transmission requirements.
FIG. 4 is a diagram intended to illustrate an example of means
which may be used in a mobile radiocommunication network entity,
noted 45, and in a mobile station, noted 46, to perform a method
according to the present invention, for downlink power control.
A mobile station 46 (or User Equipment UE in UMTS) may comprise,
for performing said method in said downlink transmission direction
(and further to other classical means not mentioned here): means 48
for, upon the occurrence of a change in said transmission
requirements, bypassing said adjustment algorithm by applying a
corresponding change to said transmission quality target value, so
as to adjust it in an anticipated way.
Mobile station 46 may also comprise, for performing said method in
said downlink transmission direction (and further to other
classical means not mentioned here): means, also noted 48 for, upon
the occurrence of a change in said transmission requirements,
bypassing said power control algorithm by applying a corresponding
change to said transmit power, so as to control it in an
anticipated way.
Such corresponding changes, corresponding to such changes in the
trasmission requirements, may for example have predetermined
values, which may for example be determined according to any of the
above mentioned possibilities.
In one embodiment, mobile station 46 may comprise: means 48' for
recording said corresponding changes.
In another embodiment, mobile radiocommunication network entity 45,
such as in particular BTS for "Base Transceiver Station" (or Node B
in UMTS) and /or BSC for "Base Station Controller" (or RNC for
"Radio Network Controller" in UMTS), may comprise, for performing
said method in said downlink transmission direction (and further to
other classical means not mentioned here): signalling means 47 for
signalling said corresponding change to mobile station 46.
Mobile radiocommunication network entity 45 may also comprise:
signalling means, also noted 47, for signalling to a mobile station
the occurrence of a change in the transmission requirements.
Advantageously, mobile radiocommunication network entity 45 may
comprise: signalling means (also noted 47) for signalling said
corresponding change to mobile station 46, together with the
signalling of the occurrence of a change in the transmission
requirements.
The present invention may be applied to any case of occurrence of a
change in the transmission requirements, such as for example any of
the above mentioned cases, or any combination of a plurality of
such cases.
The present invention is however of particular interest together
with the use of compressed mode, as now more particularly
described.
In order to keep the signaling as low as possible, the target SIR
increase due to the increased instantaneous bit rate and the target
SIR increase due to degraded performances in compressed frames may
be separated, which may be written:
Since the bit rate variation will be known by the UE, only the
additional target SIR increase .delta..sub.SIR due to degraded
performances during compressed frames may be signaled. The
signaling overhead can be low if this variation is signaled with
other compressed mode parameters (including transmission gap
length, periodicity, . . . ). For example, 2 bits could enable to
signal the following values of .delta..sub.SIR : 00: 0 dB 01: 0.5
dB 10: 1 dB 11: 2 dB
Alternatively, .DELTA..sub.SIR could be directly signaled, but a
larger number of bits would be required.
The UE will have to increase the target SIR by .DELTA..sub.SIR just
before the compressed frames (or just after the transmission gap of
the compressed frames) and decrease it back by the same value just
after the compressed frames. This target SIR variation is done
additionally to the usual downlink outer-loop algorithm that will
have to take it into account. The Node B may increase
simultaneously its transmit power by the same amount before the
compressed frame and decrease it just after the compressed frames
in order for the downlink received SIR to be as quickly as possible
close to this new target SIR.
Moreover, at least when the transmission gap is at the end of the
compressed frame, the performances in the recovery frames can also
be degraded because of the power control interruption during the
transmission gap. Therefore, it would be also desirable to increase
the target SIR in recovery frames and to signal this target SIR
increase to the UE. Alternatively, the same value (.delta..sub.SIR)
as for compressed frames could be used in order to decrease the
required signaling.
Besides, said signalling may be performed for each compressed
frame.
Alternatively, in the case where compressed frames occur
periodically, said signalling may be performed once for all, for
all compressed frames of a thus defined period, in order to reduce
the required signalling.
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